US2025356473A1PendingUtilityA1
Bridge in-service geometric form recognition method based on multi-point cloud fusion
Est. expiryFeb 27, 2043(~16.6 yrs left)· nominal 20-yr term from priority
G06V 10/803G06V 20/64G01M 5/0008G06T 2210/04G06T 17/00G06T 2210/56G06T 7/0002G06T 2207/10028G06T 2207/30184G06T 2200/04G06T 7/73Y02T90/00G01B 11/002
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Claims
Abstract
A bridge in-service geometric form recognition method based on multi-point cloud fusion comprises: defining a bridge in-service geometric form; obtaining multi-point cloud data of a bridge girder in different service periods under the condition of not stopping traffic; converting bridge three-dimensional point cloud data obtained by multiple times of scanning to a same coordinate system; fusing the point cloud data obtained by multiple times of scanning using a regional point cloud fitting algorithm to obtain a continuous and smooth theoretical girder point cloud reflecting a true spatial form of a bridge; and extracting three-dimensional coordinates of all points at any target transverse position in the theoretical girder point cloud in a span extension direction to obtain the bridge in-service geometric form.
Claims
exact text as granted — not AI-modified1 . A bridge in-service geometric form recognition method based on multi-point cloud fusion, comprising the following steps:
S 1 , defining a bridge in-service geometric form to be detected: a geometric form of a bridge girder constructed by three-dimensional coordinates of all points extracted at any of target transverse positions in a theoretical girder point cloud in a span extension direction; S 2 , performing multiple times of three-dimensional laser scanning on a bridge structure in different service periods to obtain multi-point cloud data of the bridge girder in the different service periods under a condition of not stopping traffic, and converting the multi-point cloud data to a same target coordinate system; S 3 , fusing the multi-point cloud data of the bridge girder obtained in the S 2 using a regional point cloud reconstruction algorithm to obtain a continuous and smooth theoretical girder point cloud reflecting a true spatial form of a bridge; and S 4 , extracting the three-dimensional coordinates of all points at any of the target transverse positions in the theoretical girder point cloud obtained in the S 3 in the span extension direction to obtain the bridge in-service geometric form to be detected.
2 . The bridge in-service geometric form recognition method based on multi-point cloud fusion according to claim 1 , wherein the S 2 comprises following sub-steps:
S 201 , in the different service periods, continuously performing N times of the three-dimensional laser scanning on a target bridge at a same detection station, and revising the bridge in-service geometric form to be detected according to temperature; and
S 202 , converting the multi-point cloud data to the same target coordinate system, wherein coordinate axes of two horizontal planes in the same target coordinate system are parallel to a longitudinal direction or a transverse direction of the bridge.
3 . The bridge in-service geometric form recognition method based on multi-point cloud fusion according to claim 2 , wherein the S 3 comprises following sub-steps:
S 301 , equally dividing each of N girder point clouds obtained by the N times of the three-dimensional laser scanning into m=l z /l p longitudinal regions in the longitudinal direction of the bridge, wherein l z is a bridge span, and l p is a length of the longitudinal regions in the longitudinal direction of the bridge; performing regional multi-point cloud fusion on points in each of the longitudinal regions using the regional point cloud reconstruction algorithm;
S 302 , for a J th longitudinal region in point cloud data obtained by the N times of the three-dimensional laser scanning, forming an algorithm input point set P J by all points in the J th longitudinal region, wherein l 1J , l 2J . . . l nJ , J∈{1, 2 . . . m}, and a joint of cross-sections of every two adjacent longitudinal regions is a union set of all points in the cross-sections of the two adjacent longitudinal regions;
S 303 , performing regional multi-point cloud fusion on points in each of the longitudinal regions using the regional point cloud reconstruction algorithm, including calculation of three key parameters of the bridge girder: a transverse position of the bridge girder, a spatial form of a longitudinal central axis, and spatial torsion forms of end cross-sections, to obtain a theoretical girder point cloud of each of the longitudinal regions so as to form a bridge cross-sectional framework comprising multiple girder cross-sections; and
S 304 , according to the bridge cross-sectional framework obtained in the S 303 , obtaining the continuous and smooth theoretical girder point cloud reflecting the true spatial form of the bridge using a grid point cloud generation method.
4 . The bridge in-service geometric form recognition method based on multi-point cloud fusion according to claim 3 , wherein the S 303 comprises following sub-steps:
S 303 - 1 , establishing a vibration center theory: every time any one position or part B b of the bridge is captured by a scanner to form a spatial coordinate point or point set P b in a point cloud, a probability that P b becomes closer to B b is always greater than a probability that P b becomes farther away from to B b , that is, the bridge or a part of the bridge is always located at a vibration center of the corresponding point cloud;
S 303 - 2 , based on the vibration center theory, determining the transverse position of the bridge girder in the longitudinal regions using a stepwise capture algorithm:
constructing a horizontal rectangular search box with a length l p and a width being a design width d of the bridge girder, calculating an actual maximum transverse width d m of the point cloud, and extracting longitudinal and transverse coordinates of all points in a point set P J to form a planar two-dimensional point set
P
J
xy
;
transversely moving the horizontal rectangular search box by a distance ζ, wherein during a moving process, the horizontal rectangular search box and the longitudinal regions are kept identical in length in the longitudinal direction and kept parallel in direction; recording a number n h of points in the horizontal rectangular search box after the horizontal rectangular search box is moved by h steps, wherein ζ≤(d m −d)/10; when n h satisfies:
n
h
>
n
h
-
1
,
n
h
-
2
,
n
h
+
1
,
n
h
+
2
(
1
)
determining a position of the horizontal rectangular search box having a maximum number of the points located therein as the transverse position of the bridge girder;
S 303 - 3 , based on the vibration center theory, calculating the spatial form of the longitudinal central axis of the theoretical girder point cloud of the longitudinal regions:
because the longitudinal central axis of the bridge girder in the longitudinal region is a longitudinal bisectrix of the bridge girder and the transverse position of the bridge girder has been determined in the S 303 - 2 , extracting longitudinal and vertical coordinates of all points, located on the longitudinal bisectrix of the bridge girder, in the point set P J according to the design width d of the girder to form a two-dimensional point set
P
JC
xz
;
forming a quasi-quadrangular area with a longitudinal length and a vertical height by points in the two-dimensional point set
P
JC
xz
,
wherein a maximum vertical height of the quasi-quadrangular area is denoted as h max ; according to the vibration center theory, determining a line with a slope k, moving the line in a vertical direction by a distance η k , and if a number n k of points swept by the line is greater than a number n q of points swept by lines l q with other slopes when the lines l q are moved in a same way, determining l k as the longitudinal central axis;
determining the spatial form of the longitudinal central axis l k using a stepwise capture method: creating a rectangular capture region R b with a vertical height w, an infinite longitudinal length and an initial slope k=0, wherein ω≤h max /10; moving R b from bottom to top with a step size ε, wherein an initial position of R b is denoted as Π 0 , and a position of R b after R b is moved by i steps is denoted as Π i ; recording a number of points, located in R b , in the two-dimensional point set
P
JC
xz
after R b is moved by the i steps, wherein ε≤ω/5; when n i satisfies:
n
i
>
n
i
-
1
,
n
i
-
2
,
n
i
+
1
,
n
i
+
2
(
2
)
further determining a vertical dip angle of the longitudinal central axis based on a position of R b ;
denoting a part, passing through the two-dimensional point set
P
JC
xz
,
of R b as R bp ; based on a center point of R bp , clockwise or anticlockwise rotating R b with a step size δ k ; recording a number n c of points in R b at the initial position, a number
n
j
s
of points, located in R b , in the two-dimensional points set
P
JC
xz
after R b is clockwise rotated j times, and a number
n
j
n
of points, located in R b , in the two-dimensional point set
P
JC
xz
after R b is anticlockwise rotated j times, wherein δ k ≤π/360; when,
n
c
<
n
1
s
,
n
2
s
and
n
c
>
n
1
n
,
n
2
n
(
3
)
only clockwise rotating R b subsequently; when,
n
j
>
n
j
-
1
,
n
j
-
2
,
n
j
+
1
,
n
j
+
2
(
4
)
determining a vertical bisector of R bp as the spatial form of the longitudinal central axis of the longitudinal region;
when,
n
c
>
n
1
s
,
n
2
s
and
n
c
<
n
1
n
,
n
2
n
(
5
)
only anticlockwise rotating R b subsequentially; when,
n
j
>
n
j
-
1
,
n
j
-
2
,
n
j
+
1
,
n
j
+
2
(
6
)
determining the vertical bisector of R bp as the spatial form of the longitudinal central axis of the longitudinal regions; and
S 303 - 4 , based on the vibration center theory, calculating the spatial torsion forms of end cross-sections of the theoretical girder point cloud of the longitudinal regions: respectively extracting transverse and vertical coordinates of all points, located on cross-sections of two ends of the girder, in the point set P J to form two-dimensional point sets
P
JS
xz
and
P
JE
xz
;
wherein, according to the S 302 , the joint of the cross-sections of the every two adjacent longitudinal regions shares a point set, so except an initial cross-section of a first longitudinal region and a terminal cross-section of a last longitudinal region, points of other cross-sections include points of the two adjacent cross-sections, specifically, during point selection, a width of the terminal cross-section of a prior longitudinal region and a width of the initial cross-section of a next longitudinal region are both set to d J /2, a union set of selected points is used as a two-dimensional point set of a cross-section of a joint of the two adjacent vertical sections, that is,
P
JS
xz
=
P
J
-
1
,
E
xz
,
j
∈
{
2
…
m
}
(
7
)
where
P
JS
xz
is a point set of the terminal cross-section of the J th longitudinal region, where, and
P
J
-
1
,
E
xz
is a point set of the initial cross-section of a (J+1) th longitudinal region;
because the spatial form of the longitudinal central axis of the longitudinal region has been determined in the S 303 - 2 , determining the torsion forms of the end cross-sections based on the point set
P
JS
xz
using the stepwise capture algorithm: creating a cross-sectional segment which is as long as a design cross-section and is assigned with a thickness τ, and taking the cross-sectional segment as a capture region R d , wherein τ≤h max /10, h max is a maximum vertical height within
P
JS
xz
;
respectively placing two cross-sectional segments of the longitudinal region to end positions of the corresponding longitudinal central axis in a horizontal form, with a midpoint of each cross-sectional segment being located at a corresponding end point of the longitudinal central axis;
denoting a part, passing through the point set
P
JS
xz
,
of R d as R dp ; based on a center point of R bp , clockwise or anticlockwise rotating R d with a step size δ d ; recording a number n c of points located in R d at an initial position, a number
n
j
s
of points, located in R d , in the point set
P
JS
xz
after R d is clockwise rotated j th times, and a number
n
j
n
of points, located in R d , in the point set
P
JS
xz
after R d is anticlockwise rotated j th times, wherein s represent clockwise, n represents anticlockwise, and δ d ≤π/360; when,
n
c
<
n
1
s
,
n
2
s
and
n
c
>
n
1
n
,
n
2
n
(
8
)
only clockwise rotating R b subsequentially; when,
n
j
>
n
j
-
1
,
n
j
-
2
,
n
j
+
1
,
n
j
+
2
(
9
)
determining a torsion form of R d at this moment as the spatial torsion form of the cross-section;
when,
n
c
>
n
1
s
,
n
2
s
and
n
c
<
n
1
n
,
n
2
n
(
10
)
only anticlockwise rotating R b subsequentially; when,
n
j
>
n
j
-
1
,
n
j
-
2
,
n
j
+
1
,
n
j
+
2
(
11
)
determining a torsion form of R d at this moment as the spatial torsion form of the cross-section.
5 . The bridge in-service geometric form recognition method based on multi-point cloud fusion according to claim 4 , wherein a process of obtaining the theoretical girder point cloud meeting a target point cloud density requirement using the grid point cloud generation method in the S 304 comprises following sub-steps:
S 304 - 1 , sequentially connecting all corresponding corner points of the girder cross-sections in the bridge cross-sectional framework by longitudinal connecting lines to form spatial areas of different parts of the girder in the longitudinal regions;
S 304 - 2 , setting a target point cloud density not less than a length q, dividing all segments and longitudinal connecting lines in the spatial areas by the length q, and sequentially connecting corresponding segmenting points on every two adjacent girder cross-sections and corresponding segmenting points on the longitudinal connecting line between every two girder cross-sections to form a point cloud grid finally; and
S 304 - 3 , generating at least one point coordinate at a stochastic position in each point cloud grid, and taking a set of all generated point coordinates as the continuous and smooth theoretical girder point cloud reflecting the true spatial form of the bridge.
6 . The bridge in-service geometric form recognition method based on multi-point cloud fusion according to claim 3 , wherein in the S 301 , l p ≤l z /100.
7 . The bridge in-service geometric form recognition method based on multi-point cloud fusion according to claim 1 , wherein when the N times of three-dimensional laser scanning are performed in the S 201 , N is greater than or equal to 5; during scanning, a temperature difference between any two times of scanning is less than 3° C.; scanning times and temperature conditions corresponding to bridge point cloud data in different service periods are identical; and when the temperature difference between two times of scanning in different service periods is greater than a preset temperature difference threshold, the bridge in-service geometric form is revised according to actual temperature during the two times of scanning.
8 . The bridge in-service geometric form recognition method based on multi-point cloud fusion according to claim 4 , wherein,
in the S 303 - 3 , when the longitudinal and vertical coordinates of all points, located on the longitudinal bisectrix of the girder, in the point set P J are extracted according to the design width d of the girder to form the two-dimensional point set
P
JC
xz
,
the longitudinal bisectrix is set to have a transverse width: the width of the longitudinal bisectrix is be greater than d b /50, wherein d b is a design width of a base plate of the girder.
9 . The bridge in-service geometric form recognition method based on multi-point cloud fusion according to claim 4 , wherein in the S 303 - 4 , when the transverse and vertical coordinates of all points, on the cross-sections of the two ends of the girder, in the point set P J are extracted respectively to form the two-dimensional point sets
P
JS
xz
and
P
JE
xz
,
a set cross-sectional thickness d j is not greater than l p /100.Join the waitlist — get patent alerts
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